Lens flares in movies don't make any sense.
The only way it can make the flare is if there's a camera involved, so if it's during a movie, the flare is essentially breaking the fourth wall.
shareThese break the fourth wall too, but can also be manipulated for artistic reasons. Film grain, low fps, motion blur, narrow depth of field, low dynamic range, limited color gamut.
Lens flares can be technical errors or art. JJ says they are art.
I really liked how JJ used lens flares in the Star Trek movies. Gave them a cool futuristic look imo.
shareI don't mind real lens flares, but I'm pretty sure most of these are CGI and not possible with real lenses and light sources. Some of them even look selectively placed. They do add a sense of intensity to the scenes though.
JJ Abrams Lens Flare Compilation https://youtu.be/ALHiJaSPrns
I'm not sure if film grain breaks the wall, because it just looks like an old film. With regards to motion blur, I'm not sure that look is intentional. We see it with a lot of digital films.
shareWell, if there is film grain there must be film in a camera. Just like lens flare in your example, film grain is a technical artefact.
Motion blur is controlled by shutter speed and is used to smooth the look of low frame rate. Without motion blur high motion scenes in 24 fps look terrible. Motion blur looks more natural, but it still reveals the artificially low frame rate the camera is set to.